This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. xc2xa7119 from the inventor""s application THERMAL-COMPRESS TYPE INK JETTING APPARATUS filed with the Korean Industrial Property Office on Nov. 4, 1999 and there duly assigned Ser. No. 48554/1999.
1. Field of the Invention
The present invention relates to an output apparatus such as an inkjet printer, or facsimile machine, etc., and more particularly to a thermal-compression type fluid jetting apparatus employed in a printer head of an output apparatus.
2. Description of the Prior Art
Generally, a fluid jetting apparatus employed in a printer head of an output apparatus such as an inkjet printer or a facsimile machine, etc., ejects ink in an ink chamber outward through a nozzle by exerting physical force to the ink chamber. Such a fluid jetting apparatus may be of a thermal type, a piezoelectric type, or a thermal-compression type in accordance with the method of exerting physical force on the fluid.
One example of a thermal-compression type fluid jetting apparatus is shown in FIG. 1. The fluid jetting apparatus includes a driving module 20, a membrane 30, and a nozzle module 40.
The driving module includes a substrate 15, an oxide film 14 laminated on substrate 15, a working fluid barrier 25 having a working fluid chamber 27, a heater 16 disposed in working fluid chamber 27, and a conductor 17 connected with heater 16.
The nozzle module includes an ink chamber barrier 45 having an ink chamber 57, and a nozzle plate 47 connected with the upper portion of ink chamber barrier 45. On the upper side of nozzle plate 47, a nozzle hole 49 is formed to permit ink in ink chamber 57 to be jetted therethrough.
The membrane is located between ink chamber barrier 45 and working fluid barrier 25. The membrane serves as a partition between the working fluid chamber and the ink chamber.
The working fluid such as a heptane or the like, is charged in working fluid chamber 27, while ink is constantly fed into ink chamber 57 from an ink source (which is not shown in the drawings).
FIGS. 2 and 3 show an operating process of a conventional ink jetting apparatus of FIG. 1. As electricity is applied to conductor 17, heat is generated from heater 16, and working fluid in working fluid chamber 27 is heated, forming bubbles. The bubbles cause pressure in working fluid chamber 27 to increase. Accordingly, membrane 30 is upwardly expanded, pressuring ink in ink chamber 57. Accordingly, the ink in ink chamber 57 is jetted through nozzle holes 49.
Then, as the electricity supply to heater 16 is ceased, as shown in FIG. 3, bubbles B contract. Accordingly, membrane 30 recovers its initial shape, and pressure in ink chamber 57 is decreased. The ink expressed outward through nozzle hole 49 is separated from the ink in the form of an ink drop I, and is jetted out of ink chamber 57. In this way, ink jetting is performed by the repetitious heating operation of heater 16.
Bubbles B are produced by the heat energy at different temperatures depending on the material type used as the working fluid. For example, according to the Homogeneous Nucleation theory, heptane produces bubbles at the temperature of 214xc2x0 C., while water produces bubbles at the temperature of 270-310xc2x0 C. In order to perform a repetitious printing operation, heater 16 of the ink jetting apparatus undergoes numerous heating and cooling processes, which means that the high cooling speed of heater 16 determines the high quality of the ink jetting apparatus.
In a conventional ink jetting apparatus, when heater 16 begins the heating operation, the bubble B is produced instantly, and covers the whole area of the heater 16 as shown in FIG. 2. Here, since a bubble B has low heat conductivity, when the electricity supply to heater 16 is ceased, bubble B contracts from the farthest area from where the bubble is in contact with heater 16. Accordingly, it takes a longer time for bubble B to disappear than to be produced, and the ink jetting apparatus can not be operated rapidly. In the event that heater 16 re-starts the heating operation before the complete disappearance of bubble B, the pressure control in working fluid chamber 27 is disturbed by the presence of bubble B, and the stability in driving the ink jetting apparatus deteriorates.
Accordingly, an object of the present invention is to provide an ink jetting apparatus capable of performing high-speed printing operations by providing for rapid disappearance of the bubbles during the heating operation of the heater.
The above object is accomplished by a thermal-compression type ink jetting apparatus according to the present invention, including: a nozzle module having an ink chamber for reserving ink, and a nozzle hole for permitting ink in the ink chamber to be jetted therethrough; a driving module having a working fluid chamber charged with the working fluid, a heater disposed in the working fluid chamber, a conductor for supplying electricity to the heater from an external power source, and at least one fin located on the heater and heated by the heater; and a membrane serving as a partition between the ink chamber and the working fluid chamber, the membrane being curved into the ink chamber by the pressure of a bubble which is produced while heating the working fluid to jet the ink in the ink chamber through a nozzle hole.
The fins are in the shape of plates, and are arranged on the heater in a parallel, or latticed arrangement. Preferably, the fins have a height of less than 70% of distance between the heater and the membrane, and are made of metal such as aluminum, copper, nickel, silver, or gold.
According to the present invention, since the bubbles are divided by a plurality of fins located on the heater, they disappear rapidly. As a result, high-speed driving of the ink jetting apparatus becomes possible, and stable driving of the ink jetting apparatus is performed.